r HAITI-IK. 13 



however, alluvial prairies along these streams, timberless, 

 and for the most part sandy and coarse grained, and en- 

 tirely different in composition and texture from the usual 

 Illinois upland prairies. 



The swamp lands of Whiteside, Lee and Carroll counties 

 afford a fine illustration of Professor LESQI ERE rx\s theory 

 of the gradual transformation of swampy, boggy ponds, 

 marshes and swales, into the black, spongy molds of our 

 richest prairies. Aquatic vegetation, the gradual encroach- 

 ment of the land into ponds, the slow drying of our wet 

 lands, and the gradual tilling up of the ponds by successive 

 growths and decays of aquatic vegetation, is building up, 

 rapidly, sour-soiled, treeless prairies. The processes are 

 similar to those forming the peat beds. The results of the 

 processes are curtailed and modified, and a peaty-soiled 

 prairie is formed, instead of a bog or bed of peat. 



But the high, rolling prairies of Carroll, Stephenson, 

 AVinnebago, and parts of Ogle and AVhiteside counties, with, 

 in many instance's, but thin soils covering the coarser drift 

 materials helnw, do not show so plainly the same sort of 

 originating causes. They are interspersed with numerous 

 small groves of timber. These grow along the alluvial 

 mixed soil of the streams, and upon the ridges and patches 

 thrown up and beat together by the waves and currents of 

 the broad lake-like expanse of water, which covered this 

 part of the State immediately subsequent to the glacial ice 

 period. A few of these drift ridges, as in north-western 

 Ogle county, are treeless, owing perhaps to fires, or other 

 local cause--. 



Excessive 1 humidity of these high, rolling, somewhat 

 sandy prairies does not exist, and cannot satisfactorily ac- 

 count for their treeless character. Xeither do they bear in 

 their soils and subsoils the evidences of having once been 

 swampy, marshy plains. 



When the waters of the broad shallow fresh-water sea, 

 once extending south and west of Lake Michigan, were 



